The present invention relates to a fuel pump and filter assembly for an engine, in particular a compression ignition (diesel) engine.
In a diesel engine operating with a high pressure common rail (HPCR) fuel system, a low pressure supply pump draws fuel from the fuel tank and supplies it to a high pressure pump that pressurises the common fuel rail. It is not desirable to place the fuel filter on the suction side of the low pressure pump because low pressure supply pumps, such as gear, gerotor and vane pumps, are not capable of generating high suction without the risk of cavitation. Consequently, the fuel filter is normally positioned between the low pressure supply pump and the high pressure pump.
In an HPCR pump in which the low pressure supply pump is incorporated within the same unit as the high pressure pump, the filter is positioned remotely and fuel lines are needed to route the fuel from the outlet of the low pressure pump to the fuel filter and then back from the filter to the inlet of the high pressure pump. These lines, or tubing, make for high assembly and component costs. In certain applications, for example in an agricultural vehicle, exposed tubes also risk being hit by objects in the field, thereby incurring greater maintenance costs.
The present invention aims to mitigate the foregoing disadvantages by reducing the external pipework required to connect the low and high pressure pumps to one another through a fuel filter.
According to the present invention, there is provided an assembly comprising a pump unit incorporating an engine driven low pressure pump for drawing fuel from a reservoir and an engine driven high pressure pump connected to supply fuel drawn by the low pressure fuel pump under pressure to a common fuel rail, and fuel filtering means connected in the fuel flow path between the low pressure and the high pressure pump, characterised in that the fuel filtering means comprises a fuel filter head connected directly to, the housing of the pump unit and including a plate for mounting a filter containing a filtration element, the fuel filter head being formed with a first internal flow passage to enable fuel pressurised by the low pressure pump to be supplied to one side of the filter element and a second flow passage connected to the other side of the filter element to enable the filtered fuel to be supplied to the high pressure pump.